This invention relates generally to containers which store and dispense film units of the self-developing type.
Self-developing film units of the kind used in instant photography are typically housed in a film pack cassette having a yieldable supporting platform for supporting a stack of such film units. Representative examples of these kinds of film packs or assemblages are disclosed generally in U.S. Pat. Nos.: 3,821,049; 3,707,116; 3,607,279; 3,874,875; 4,172,650; 4,201,457; 4,226,519; and 4,492,445 which are assigned in common herewith. The supporting platform, in general, urges each of the topmost units against the interior of a top wall defining an exposure aperture of the cassette. Included is a removable dark slide which covers the exposure aperture to prevent fogging of the film units prior to insertion of the pack into the camera. After the dark slide is removed, the top film unit may be exposed. Following exposure a camera pick mechanism serves to advance the film unit exteriorly of the film cassette. Thereafter, the pressure applying rolls withdraw the film unit from the cassette and commence processing.
It is important that only a single film unit be dispensed from the film cassette following exposure. It is also important that actinic light be prevented from penetrating the cassette and fogging the film units.
In practice there are a number of cassette and camera features which are aimed at achieving these functions. In terms of the cassette, the leading end wall thereof is coupled hingedly thereto and movable upwardly to a closed position after the contents have been inserted. The top of this end wall in conjunction with the cassette top wall defines a film withdrawal slot which is located in operative relationship with respect to the topmost film unit. For attempting to prevent more than a single film unit from being withdrawn there is provided a hold-back finger. The hold-back finger is formed on the end wall and projects part way across the withdrawal slot so that its top surface defines a clearance which is intended to allow only a topmost film unit to be ejected.
For preventing actinic light from entering the cassette there is provided among other features a flexible light seal. The light seal tends to cover the exit slot, but can be displaced by an advancing film unit or dark slide which emerges from the cassette. The flexible light seal tends to prevent light from penetrating the slot and thereby fogging the film.
It is evident that it is extremely important that the hold-back finger be properly positioned to insure emergence of only a single film unit. Understandably, even relatively small variations in the proper positioning of the hold-back finger can result in the latter not serving to preform its intended functions.
Positioning problems can arise given the typical method of attaching the leading wall to the container or cassette body. More specifically the leading wall is usually bonded, as by ultrasonic welding, to the cassette body. Sometimes given the machine handling requirements of such welding there is a tendency for the hold-back finger to walk from its intended position. Thus mispositioning arises.
One attempt at sealing the end wall to the cassette body without welding is to rely upon a latching arrangement. In this approach there is provided a pair of latch posts or projections integrally formed on the cassette and arranged to cooperate with openings formed in adjacent ends of the leading end wall. The posts cooperate with these projections to position the hold-back finger. The positioning of the latch post in this known approach is arranged in such a manner that there exists a possibility that actinic light might enter the cassette body, thereby fogging the film units. With this latching arrangement, there is a possibility that the leading wall might be latched to the cassette body without properly positioning the hold-back finger.